Blocking execution of non-exec things

[Kees Cook]

Hello!

As part of implementing the "Execute-Permission Bit Required" policy[1], I
need to make changes to a few MIME handlers and to the nautilus .desktop
file handler.

The main issue is that of the error message to produce, and I'm hoping to
get some input for that from the Desktop team.

Thanks,

-Kees

[1] https://wiki.ubuntu.com/SecurityTeam/Policies#Execute-Permission%20Bit%20Required

-- 
Kees Cook
Ubuntu Security Team